An organic electronic device means a device that requires exchanging of electric charges between electrodes using holes and/or electrons and organic materials. The organic electronic device may be largely divided into the following two devices depending on the operation principle. First, the organic electronic device is an electric device in which an exciton is formed in an organic material layer by a photon that flows from an external light source to the device, the exciton is dissociated into electrons and holes, and the electrons and the holes are each transferred to different electrodes and used as a current source (voltage source). Second, the organic electronic device is an electronic device in which holes and/or electrons are injected into an organic material semiconductor, which forms an interface with an electrode, by applying voltage or current to two or more electrodes, and the device is operated by the injected electrons and holes.
Examples of an organic electronic device include an organic light emitting device, an organic solar cell, an organic transistor, and the like, and these all need a hole injection or transporting material, an electron injection or transporting material, or a light emitting material for driving the device. Hereinafter, an organic solar cell will be mainly described in detail, but in the organic electronic devices, a hole injection or transporting material, an electron injection or transporting material, or a light emitting material is operated under similar principles.
A possibility of an organic solar cell was first presented in the 1970s, but the efficiency thereof was so low that the organic solar cell had no practical use.
However, C. W. Tang of Eastman Kodak showed the possibility of commercialization as various solar cells with a double layer structure using copper phthalocyanine (CuPc) and perylene tetracarboxylic acid derivatives in 1986, and then interests in organic solar cells and related researches have rapidly increased, thereby bringing about a lot of advancement.
Since then, organic solar cells have made the breakthrough in terms of efficiency of the organic solar cell as the concept of bulk heterojunction (BHJ) was introduced by Yu et al. in 1995, and fullerene derivatives of which the solubility is improved such as PCBM have been developed as an n-type semiconductor material.
Since then, studies have been continuously conducted in order to increase the efficiency of an organic solar cell.